Trans ID

[Licensed to kill]

I have a duplex and a triplex trans and am trying to identify which models they are. Not finding anything on either that corresponds to the model numbers I have found online. Anyone know where to look and what to look for?. 

[terry]

Look on left side of front box, right behind fill plug, might have to wire brush it real good to see, duplex will be a Trd 72 direct or a 720 overdrive, triplex will be a trt 72 or 720.  Terry

[Licensed to kill]

Thanks Terry. found the ID in the triplex (TRTL72) but nothing on the duplex. Ran the numbers and the ratios in the triplex will work if it is in good shape. Will pull it apart in the next few days and check it out. 

[terry]

21 hours ago, Licensed to kill said:

Thanks Terry. found the ID in the triplex (TRTL72) but nothing on the duplex. Ran the numbers and the ratios in the triplex will work if it is in good shape. Will pull it apart in the next few days and check it out. 

should be aluminum rear box, and direct in the front box, be sure to check countershaft end play, dial indicator through PTO opening, there are shims under back box cover plate on the end of countershaft.  Terry  I think i used the PTO gear to do this.

Edited October 15, 2023 by terry

[Licensed to kill]

I talked to the guy that used to own a dealership and was a Mack mechanic and he said that I can just take the bolts off the rear box and it comes right off. I will also open up the top and look inside. I looked in the side cover hole and while there is gunk in the bottom of the box, the gears look good from what I can see. I was/am concerned as the PTO cover was missing and there was a mouse nest in the trans when I got it, been open like that for about 30 years. With the bottom gears looking good from the PTO opening, I am encouraged that the rest might be good but we will see. So, checking end play, is that done just on the gear and can that be done with the rear box removed out have to be done before removing it?.  

[terry]

When you set the endplay on the countershaft both boxes need to be bolted together, there is a tapered bearing between them, so when you check end play it is for both countershafts, it would be the last thing to do on reassembly.   Terry

[Vladislav]

Almost as Terry said above. You set end play for both main and compound countershafts together. Of how to identify a tranny the way could be opening the top covers (which worth to do anyway before anything else) and figure it's duplex or triplex and direct or over just by looking at the gears. 

[terry]

As far as telling a duplex, triplex or quad. Back box length will tell you.   Terry 

[Licensed to kill]

What should the end play be?

[Joey Mack]

I think its .003'' - .005''.............  I will try to find my TRD72 book..  Hell, I just built one a year and a half ago..  

[Licensed to kill]

20 hours ago, terry said:

should be aluminum rear box, and direct in the front box, be sure to check countershaft end play, dial indicator through PTO opening, there are shims under back box cover plate on the end of countershaft.  Terry

Just to be clear, could you walk me through how exactly the end play shouldn be measured through the PTO hole?. Specifically, how/where to set the dial indicator and how to move the shaft fore and aft to find the play. 

[terry]

Been along time since i have done this, but take a dial indicator with a magnetic base and mount it somewhere around PTO , find a fixed gear on countershaft , configure indicator to touch it, take a small pry bar to slide fixed gear forward and back to check end play, then there are shims under countershaft rear cover piece to add or take out shims for desired endplay. Joey might have a different way to measure this.  Hope this helps     terry Think i used the PTO gear to do this

 

Edited October 15, 2023 by terry

[Joey Mack]

Sounds good.  my guess is the trans in still in the truck. A fixed gear for sure, however , all the counter shaft gears are pressed on, so any move of the gear is already an issue. I will go try to find my book for the spec.. 

[terry]

For some reason I thought the PTO gear was fixed, if nothing else it can be done on the tail end of countershaft with the rear cover off. But I think the PTO gear is pressed on so tight you don’t have to worry about it moving to check this.  Terry

Edited October 15, 2023 by terry

[Licensed to kill]

Trans is not in the truck. In fact, I just retrieved it and brought it into the shop and power washed it. I don't think going through the pto cover will work well as, being an aluminum case, mag base on the dial indicator won't work so well 😁. The rear box is cast iron, looks "HEAVY". Would like to remove it to see what is inside condition wise but will have to figure out how I want to do that without dropping it on my foot or something along those lines.  Will be opening up the top for sure to have a look. One PTO cover was missing and I removed the other to blow all the gunk out of the case through the two openings, came nice and clean and the gears that are visible looks nice and clean also. Sprayed everything I could see down with WD-40 to displace the water and prevent flash rusting. SOOOOO, If I understand correctly, I can remove the rear counter shaft cover and check the play there??.....still by prying back and forth on a gear through the PTO hole?. Counter shaft held in at the back with a snap ring or........?

[terry]

Yeah rear box will work to, some don’t have PTO openings, the rear bearing on rear countershaft is held in by a tapered bearing towards the front, the rear cover  and shims press on the bearing outer race to set endplay. Hope I’m explaining this so you understand?   Terry no snap rings

Edited October 15, 2023 by terry

[Joey Mack]

LTK,,,  I looked in my svc. manual cabinet ,,TWICE,,,  I can not find my TRD-72 book..   I'm sorry, and not Happy about this..  My books are ''Gold'' to me..  anyway,  You got this..  Jojo

[terry]

Joey I looked in one of my old Mack manuals it says on reassembly leave top main shaft out of back box bolt cases together and wrap string around counter shaft and set at so many pounds pull, I never done that to much crap! I used the dial indicator after assembled and set at so many thousands but I don’t remember the exact number.  Terry

Edited October 15, 2023 by terry

[Joey Mack]

OK..  I get it...  it's probably 3-6 lbs for new bearings and 2-5 lbs on re-used bearings..  You use a 'Fish scale' to pull the string.. and read the scale..  I was taught that method when I used to build Mack rears..   it checks pre-load...   not end play..  Jojo

[terry]

But when you preload does that take all your end play away?  Yeah them figures for new and used bearings are right on, I never used the string and scale, I used the dial indicator, don’t remember how many thousands though.  Terry

Edited October 15, 2023 by terry

[Joey Mack]

yes, pre-load is the opposite of end play..  Mack uses pre-load,  well at least on what I used to re-build,  Eaton used endplay,,  so when you feel a small amount of movement in an Eaton rear input/output, or tranny output, it is correct,,, 

[Licensed to kill]

Opened up the top of both boxes on the triplex and everything looks good. No rust, all the gears look nice and everything turns nice and smooth just needs a good flush. Will check the end play on the counter shaft and shim accordingly if required and cross my fingers that it will be good I guess. 

[Joey Mack]

since it is out of the truck, you can stand it on its nose.  this will allow the shafts to drop into front bearing cups. then you can check both cases.  the front case through a side cover, and you can remove the bearing caps on the rear and dial indicate the ends of the shafts.  jojo

[Vladislav]

I did that end play setting procedure on TRD-37. Mostly similar to TRD72, just a bit older and doesn't have a sliding clutch for the 1st gear so you put the mesh in just by the gear itself, the same way as the reverse. 72's were improved a bit about that but the rest seemed very similar judging but the books.

So the end play of the countershaft was prescribed to be checked with a dial indicator set against the front end of the main counter shaft. You remove the front cover of that shaft from the cluch side of the tranny. The matter is the front bearing is a cylindrical roller bearing, not a cone. So can float. The rear bearing of the front countershaft is a double cone. The front cone sets against a race installed in the main case rear wall when you forse the shaft up front (the cone oriented to the front). Behind it, also on the rear end of the main shaft the 2nd cone installed, but oriented to the rear. And the compound box countershaft's front bearing race sets against that 2nd cone. The rear end of the compound countershaft has its rear bearing race in the rear wall of the compound housing where you can load it up front with the outside bearing cover. And the grade of the affect is limited by the shims pack.

This way you remove all the shims, fit the rear cover and slightly tight up a couple of nuts. Pry the main shaft through the PTO hole and look for the movement of the front end with the indicator. Turn nuts tighter to forse both the shafts to move to the front and see lesser readings. When you're withing the desired figure measure the gap between the rear cover and the housing with a filler gage and use a shim pack that thick.

The book I have points out a 0.000-0.002" end play. That tranny is a predecessor of 72 series and my particular unit was made in 1945. But overall the design looks very similar so I guess those figures should work.

[Licensed to kill]

Finally found the time to flush out the trans case and check the counter shaft end play. .027, a bit much I'm thinkin'. So, to take upon that slack I remove the front counter shaft cover and remove shims until I get to....what.....002 -.005 ???. The cover is recessed so using a feeler gauge like Vlad suggested would be difficult so thinking I can measure the shim pack with a micrometer, subtract .025 and try that. Thoughts before I go forward?. If I do this it should be set for both counter shafts (main and aux boxes) IIUC.